Topical Products and their Critical Quality Attributes ABSTRACT The microstructure in topical products is highly influenced by the manufacturing process variables. The microstructural differences between products with or without same composition could be investigated by evaluating certain critical quality attributes of the product. The critical quality attributes also influence the product performance in vivo. Therefore, there is need for a systematic investigation to understand the potential failure modes, the reasons, the quality attributes that are critical in determining the product performance and manufacturing process variables. From the regulatory perspective, Q3 difference could possibly exist between the products even when the products are Q1 and Q2 equivalent. We propose two specific aims in this project to address the above discussed areas. In aim 1 we propose to classify the topical formulations based on their nature and composition. To identify the potential failure modes for each class and to identify the quality attributes that are critical in determining the product performance in vivo. To identify the most appropriate methods for measuring the physical and chemical properties of the topical product is also one of the goals. In aim2 we propose to investigate the effect of process variables on the critical quality attributes (CQAs) and the performance attributes of the product. We also propose to establish design space for each class of the products using QbD approach.